Medical device testing apparatus

ABSTRACT

An apparatus ( 30 ) that can test external components of a cochlear implant system in a manner that does not require the person conducting the test to have advanced knowledge of the operation of the tested component. The apparatus provides a relatively quick and straightforward answer to the question of whether the component is operative or not. The testing apparatus ( 30 ) comprises at least one testing station ( 32,33,34 ) for receiving the component to be tested and makes an electrical and/or inductive connection thereto. A testing circuit is adapted to apply at least one test to the component and measure the response of the component to that test. The apparatus ( 30 ) compares the response of the component to stored data indicative of the response to the test of at least one equivalent component that is known to be operational and outputs a result of said comparison.

The present invention is a device to assist in testing the functionalityof medical devices, such as external equipment associated with animplantable device. More preferably, the present invention is a tool toassist in the diagnosis, analysis and servicing of a cochlear implantsystem.

DESCIPTION OF THE PRIOR ART

Over recent times, the use of implantable devices to assist in restoringfunctionality to individuals who have lost the capability for thatfunction to be performed naturally by the body has become increasinglycommon. Examples of such devices include pacemakers, defibrillators,cochlear implants, hearing aids and functional electrical stimulation(FES) devices.

A typically key component of currently available implantable devices hasbeen the presence of an external controller unit to control theimplantable portion of the device. This external controller unit cancommunicate with the implantable device through a variety of means todeliver various forms of control signals to allow the implantable deviceto perform its desired function.

With regard to cochlear implants, such devices have proven successful inrestoring the sensation of hearing to individuals who have previouslybeen considered as being severely or profoundly deaf, and unable toobtain benefit from conventional hearing aid devices. In suchindividuals, the hair cells of the cochlea have been damaged and are nolonger able to transfer the mechanical vibration of the fluid inside thecochlea into electrical signals to be perceived by the brain as sound.One such cochlear implant device that has proven successful in suchcases is described in U.S. Pat. No. 4,532,930, the contents of which areincorporated herein by reference. In such a device the cochlear implantbypasses the role of the hair cells and directly delivers electricalstimulation to the nerves in the cochlea, the electrical stimulationbeing representative of speech and environmental sounds. The neuralimpulses generated by the electrical signals are then sent to the brainand interpreted as sound. The electrical stimulation is usuallydelivered to selected nerve sites within the cochlea by an array ofelectrodes, electrically connected to an implanted stimulator device.

The implanted stimulator device typically receives a coded sound signalfrom an external sound processor device, and this coded signal directsthe implanted stimulator device to deliver the appropriate electricalstimulation to the appropriate stimulation site to reproduce thecorresponding sound. The implanted stimulator is equipped withelectronic circuitry and switches to allow stimulation to be deliveredto a number of electrodes simultaneously or sequentially to providedetailed sound perception.

The external device provides a coded signal to the implanted stimulatorvia a transcutaneous link, such as a radio frequency (RF) link, and thecoded signal is directly representative of the surrounding sound asdetected by an external microphone. The external microphone may bemounted on the external device or may be remote therefrom but connectedvia a suitable link.

In general, the basic function of the external processor is to take theaudio signal from the microphone and to process it according to aparticular speech coding strategy, to produce a signal that containsstimulation information for the implant. In this regard, speechprocessors are quite patient-specific and whilst the system hardware isrelatively common for all users, the software used as well as thebenefits gained from different software packages varies considerablyfrom patient to patient.

It can therefore be appreciated that for devices such as cochlearimplants, successful operation of the device relies upon the externaland implanted portions of the device working together to produce thedesired functionality. Should any one part of the external or implantedhardware malfunction, the capacity of the device to perform its functionis severely affected. In the case of cochlear implants, this couldresult in uncomfortable or unsafe stimulation, or more commonly, in therecipient losing the capacity to detect sound.

For this reason it is important that should a recipient experienceproblems with their device, they must feel confident that the problemcan be quickly detected and where possible, resolved so that the devicecan be returned to normal operation with minimal inconvenience to therecipient.

At present, in the unfortunate event of a cochlear implant recipientexperiencing a difficulty or malfunction causing them to lose systemfunctionality, the recipient must contact a local clinic or agent thathas been assigned to deal with such issues. The clinic or agent is inmost cases familiar with the recipient's needs and requirements and hasfull records of the recipient's history and any past problems they mayhave experienced.

In most cases it has been found that the major source of system problemsand faults is related to the external system components, namely theexternal cables connecting the various external components, as well asthe external transmitter coil. This is primarily due to the fact thatthese components are exposed to everyday handling and exposure to theelements, and as such are more likely to suffer damage.

Currently, if a recipient reports a device as being faulty, the clinicor agent firstly checks the recipient's external equipment formalfunction. This is done by swapping the suspected faulty device with aknown non-faulty device and assessing whether the problem has beenresolved. This process is repeated for all cables and coils and as suchthe clinic must carry a stock of spare parts for every piece of externalequipment, which is often not economically feasible for smaller clinics.Such a process is understandably time consuming and reduces theefficiency of the clinic to deal with important and more time intensivetasks, such as implant programming sessions.

The present invention aims to address these issues.

Any discussion of documents, acts, materials, devices, articles or thelike which has been included in the present specification is solely forthe purpose of providing a context for the present invention. It is notto be taken as an admission that any or all of these matters form partof the prior art base or were common general knowledge in the fieldrelevant to the present invention as it existed before the priority dateof each claim of this application.

SUMMARY OF THE INVENTION

Throughout this specification the word “comprise”, or variations such as“comprises” or “comprising”, will be understood to imply the inclusionof a stated element, integer or step, or group of elements, integers orsteps, but not the exclusion of any other element, integer or step, orgroup of elements, integers or steps.

The present invention provides a device that can relatively simply testthe components of a medical device, such as the external components ofan implantable system, and give a direct indication as to whether thecomponent is functional or not. Such a device will be able to be used bythe recipient of the device or a clinic to diagnose problems immediatelyand avoids the need for the clinic to spend unnecessary time diagnosingand correcting such simple problems and reduce the need for them tocarry a stock of spare components for trouble shooting purposes.

According to one aspect, the present invention is a testing apparatusfor testing at least one component of a medical device and diagnosingproblems associated therewith, the testing apparatus comprising:

-   -   at least one testing station for receiving said at least one        component and making an electrical and/or inductive connection        thereto;    -   at least one testing circuit adapted to apply at least one test        to said component and measure the response of the component to        said test;    -   a memory means for storing data indicative of the response to        said test of at least one equivalent component that is known to        be operational;    -   a comparator means for comparing the response of said component        to said test to said data and determining whether said response        is at least substantially similar to said data; and    -   an output means for outputting a result of said comparison.

In one embodiment, the medical device is a tissue-stimulating devicehaving an implantable component. In one embodiment, the device can be ahearing prosthesis such as a cochlear implant system. In thisembodiment, said at least one component that is to undergo testingpreferably comprises a cable and/or a transmitter coil adapted to beconnected to an external speech processor component of a cochlearimplant system.

The testing apparatus preferably comprises a case having a first surfacehaving the testing stations as defined herein.

In one embodiment, the testing apparatus is preferably adapted to testmore than one type of component. For example, different speechprocessors can be adapted to operate with different cable and/or coilcombinations. In different embodiments, the testing apparatus can beadapted to test two, three, four, or more types of cables and/or two,three, four, or more types of cable and coil combinations. Where thetesting apparatus is capable of testing two different types of cable,the apparatus preferably has at least two testing stations for providingan electrical connection to said cables. Where the testing apparatus iscapable of testing three or more cables, the testing apparatuspreferably has at least three or more testing stations, and so on.

Each cable testing station, where there is more than one, is preferablyadapted to test only one type of cable. Where there are two or cabletesting stations, each station is adapted to test a different type ofcable from that of the other cable test stations. Each cable testingstation can comprise a socket provided in the first surface of the caseand having a shape that is adapted to receive a plug of a particularcable design and no other. Each socket design preferably allowselectrical connection to the cable under test.

Each testing apparatus can have a single coil testing station. Inanother embodiment, the testing apparatus can have two or more coiltesting stations. The coil testing apparatus preferably comprises aplanar area in the first surface of the case on which the tested coilcan be placed. The planar area can have an indicia means providedthereon that provides an indication of where the tested coil should beplaced to ensure an appropriate test of the tested coil is undertaken.In one embodiment, the indicia means can comprise a pictorialrepresentation of a transmitter coil. Where the testing apparatus isable to test more than one coil design, the planar area can have morethan one unique indicia means provided thereon. For example, the planararea can have different pictorial representations of the different coiltypes that can be tested using the apparatus.

The tested coil preferably has a magnet that aligns itself correctly onthe coil test station via another attracting magnet positioned at orbelow the planar surface of the case. The attractive force between themagnets is preferably used to maintain the tested coil in the correctplace for testing.

Each tested coil preferably has a cable extending therefrom that is alsotestable by the testing apparatus. In a preferred embodiment, a testedcoil with a cable extending therefrom is tested by positioning the coilin the appropriate location on the planar surface and then inserting theother end of the cable into the appropriate cable test socket of theapparatus.

The testing apparatus is preferably capable of sensing the type of coil,cable, or coil and cable combination that is under test and then accessfrom the memory means the appropriate stored data for use by thecomparator means of the apparatus.

In a preferred embodiment, the testing apparatus includes a controlmeans that controls the overall function of the apparatus. The controlmeans can comprise a microcontroller. The microcontroller can furtherpreferably act as the memory means for the testing apparatus. Themicrocontroller further preferably comprises a microprocessor having ananalogue to digital converter (ADC) to digitise the measurementsrepresentative of the tested component. The microprocessor is furtherpreferably adapted to run software that controls the operation of thetesting apparatus.

In a preferred embodiment, the measurements from said one or moretesting circuits are in the form of current and voltage levels.

It is envisaged that said data indicative of the response of saidequivalent operational component is preferably in the form of voltageand current ranges associated with non-faulty cables and transmittercoils used in cochlear implant systems.

In a further embodiment, the memory means is programmable to enable thestored data to be upgraded and altered according to the designrequirements of the components to be tested.

In a further embodiment, the output means comprises one or more lightsthat can be illuminated or turned off in response to the outcome of thetest. In a preferred embodiment, a light illuminates if the testedcomponent passes the test and fails to illuminate if the testedcomponent is inoperative or faulty. In one embodiment, the light can bea light emitting diode (LED), such as red LED.

In one embodiment, the LED can be adapted to only illuminate only whenthe response of said tested component is determined by the comparatormeans to be identical to the response of said equivalent operationalcomponent. It is, however, more likely that the LED can be adapted toilluminate when the voltage and/or current response of said testedcomponent is within a predetermined range of what are consideredacceptable values for that component. The predetermined range might be avariation of plus or minus 1% of the expected response. Other percentagevalues can be envisaged, eg. plus or minus 5%, 10%, 20% and so on.

In operation, the microcontroller of the apparatus can send a signal tothe coil testing circuit comprising a socket voltage driver that drivesthe coil preferably with an AC square wave voltage source at or near theresonant frequency of the coil. This resonant frequency is dependent onthe type of coil being tested. For example, in some instances it may benear 2.5 or 5.0 MHz. A simple push-pull square wave voltage drivercircuit, similar to those used in external speech processors can be usedfor this purpose.

If the coil and cable combination plugged into the device is correctlyfunctioning, a coil in the testing circuit will preferably resonatethrough an inductive coupling between the tested coil and the coiltesting circuit and the coil current will have a value determined by thecoil impedance at its resonant frequency, which is typically a few tensof Ohms, or less. In testing the coil and cable combination inaccordance with the present invention, the apparatus preferably monitorsthe coil current and if the current is found to be above an acceptablevalue, the coil and cable combination pass the test and the deviceindicates a “PASS” to the tester via illuminating the LED. If the coiland cable combination is found to be faulty (eg. the coil cable isbroken, connector faulty etc) the device indicates a “FAIL” by notilluminating the LED, or alternatively, by emitting a “FAIL” signal viaanother indicator means. In the event of a failure, most coil and cablecombinations either involve a complete failure of the circuit or adetuning of the circuit in some way. Therefore in these faultconditions, the amplitude of the coil current will be reduced below apredetermined threshold and the coil will be detected as having failed.

In a preferred embodiment, the testing circuit for the coil and cable incombination preferably comprises al voltage rectification and currentsensing circuit that measures the compliance of the coil and cablecombination and outputs the result to the microcontroller.

Where the compliance of a cable is to be tested, a DC potential can beplaced on one cable lead and the potential of another lead of the cablecan be measured. The other end of the cable is preferably plugged into aresistor load network connecting all the cable leads together. When allthe cable's leads are functioning normally a specific voltage,determined by the resistor load network, is expected on the sensed lead.If a fault occurs (one line open circuit or shorted to another) thiswill change the current flow in the cable and cause the voltage in thesensed lead to change. The voltage is preferably sensed by digitising itusing the microprocessor ADC with software used to determine whether thesensed value corresponds to a normal or a faulty cable. When a voltageis sensed which corresponds to a normal cable, the microprocessor canilluminate the LED in the manner as discussed above.

According to a second aspect, the present invention is a method oftesting at least one component of a medical device and diagnosingproblems associated therewith comprising the step of making anelectrical and/or inductive connection between said component and atleast one testing station of the testing apparatus as defined herein andperforming a test on said component.

The present invention provides an apparatus that can test externalcomponents of a cochlear implant system in a manner that does notrequire the person conducting the test to have advanced knowledge of theoperation of the tested component. It provides a relatively quick andstraightforward answer to the question of whether the component isoperative or not.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention will now be described with reference to theaccompanying drawings in which:

FIG. 1 is a pictorial representation of a conventional cochlear implantsystem;

FIG. 2 is a pictorial representation of a tester unit in accordance withone embodiment of the present invention; FIG. 3 is a block functionaldiagram of the tester unit of the present invention;

FIG. 4 is a circuit diagram showing a circuit capable of testing acoil/cable combination according to one embodiment of the presentinvention; and

FIG. 5 is a circuit diagram showing a circuit capable of testing a cableaccording to one embodiment of the present invention.

PREFERRED MODE OF CARRYING OUT THE INVENTION

Before describing the features of the present invention, it isappropriate to briefly describe the construction of a cochlear implantsystem with reference to FIG. 1.

Cochlear implants typically consist of two main components, an externalcomponent including a speech processor 29, and an internal componentincluding an implanted receiver and stimulator unit 22. The externalcomponent includes an on-board microphone 27. The speech processor 29is, in this illustration, constructed and arranged so that it can fitbehind the outer ear 11. Alternative versions may be worn on the body.Attached to the speech processor 29 is a transmitter coil 24 whichreceives electrical signals through a cable 10 and transmits signals tothe implanted unit 22 via a radio frequency (RF) link.

The implanted component includes a receiver coil 23 for receiving powerand data from the transmitter coil 24. A cable 21 extends from theimplanted receiver and stimulator unit 22 to the cochlea 12 andterminates in an electrode array 20. The signals thus received areapplied by the array 20 to the basilar membrane 8 thereby stimulatingthe auditory nerve 9. The operation of such a device is described, forexample, in U.S. Pat. No.4,532,930.

The sound processor 29 of the cochlear implant can perform an audiospectral analysis of the acoustic signals and outputs channel amplitudelevels. The sound processor 29 can also sort the outputs in order ofmagnitude, or flag the spectral maxima as used in the SPEAK strategydeveloped by Cochlear Ltd.

As previously mentioned, when a problem is reported by a cochlearimplant recipient, the clinic responsible for identifying and resolvingthe problem, often follow a systematic approach. It is established thatthere may be a number of possible causes for the problem, such as a lossof implant function, and these causes may be related to:

the external hardware;

physiological or psychological changes; or

the implanted hardware.

As the external hardware is often the simplest and most obvious sourceof problems, the clinician often starts with assessing the externalhardware for faults before consideration is given to the other tworelatively more complicated problems.

In the case of the cochlear implant as described in FIG. 1, the mainexternal components are the external sound processor 29, the transmittercoil 24, and the connector cable(s) 10. The present invention addressesa device and process to simply and quickly test the transmitter coil andconnector cables for proper electrical function, such that the clinicianor recipient can quickly solve such problems or eliminate thepossibility of such problems being a contributing factor to the reportedproblem.

In terms of the transmitter coil and cables used in cochlear implants,their function is to transmit encoded radio frequency signals from theexternal speech processor to the internal component of the implant thatis positioned beneath the recipient's skin. Therefore it is both thecoil and cable that form part of the resonant RF circuit which iscoupled to the receiver coil in the implant. The RF is typicallygenerated at either 2.5 MHz or 5.0 MHz depending upon the design of thespeech processor and implant. In operation, the transmitter coil and thereceiver coil are tuned to frequencies, for example, close to but notexactly at, either 2.5 or 5.0 MHz.

In construction, the coils usually consist of a number of turns of wire,typically around 30mm in diameter, with an injection moulded plasticcovering all components. In the centre of the coil there may bepositioned a magnet that is used to locate and hold the transmitter coilin an appropriate external position relative to the implant or receivercoil, which also has a magnet positioned therewith.

In cochlear implants produced by the present applicant, depending uponthe type of speech processor used, there may be a number of differenttransmitter coils designed to operate with each of the different speechprocessors that are or have been able to be used by cochlear implantrecipients. These coils are often not compatible with processors otherthan that which they have been designed for, and hence interchanging ofcoils may result in the implant receiving no signal, a non-meaningfulsignal, or an incomplete or garbled signal. One way of overcoming theproblem of using the wrong transmitter coil with the wrong processor hasbeen to provide different electrical connecting plugs for each coil,matching with a particular type of socket in the speech processor. Thishas also resulted in the need for a wider variety of cables connectingthe speech processor to the transmitter coil, with corresponding socketsto match the particular device.

FIG. 2 is a top view of one embodiment of the present invention. Thetester unit is represented as numeral 30 and includes a plurality oftest stations designated by reference numerals 32, 33 and 34 arranged onthe top surface of the unit 30 for testing the external coil and cablesof a cochlear implant. In test stations 32 and 33, a plurality ofconnector sockets 31 are arranged as shown with each socket in teststation 32 having a corresponding socket arranged in test station 33.The connector sockets 31 are designed to receive the various types ofcables provided with the implantable system, with each free end of acable having a plug that is connectable to the appropriate socket intest station 32 and 33, for testing. Each of the connector sockets 31are designed to receive only one type of cable plug, to ensure that thecorrect integrity test is carried out on that cable in accordance withthe operating requirements. Arranged on the top surface of the unit 30is an indicator 35, in this case an LED, which provides an indication tothe tester as to whether the cables pass the test or not. In a preferredembodiment the indicator 32 may emit a green light if the cable is OKand emit no light if the cable is faulty. Alternatively, a red light maybe emitted if the cable is found to be faulty.

Other variations may also be implemented to convey this information tothe tester, which fall within the scope of the present invention. Forexample, the word “PASS” or the word “FAIL” could be illuminateddepending on the outcome of the test.

The unit 30 also includes a transmitter coil test station 34 to enablethe transmitter coils to be integrity tested. In the embodiment as shownin FIG. 2, the transmitter coil test station 34 is positioned on theupper surface of the unit 30 to allow a transmitter coil (not shown) tobe placed thereon. The magnet of the transmitter coil to be testedaligns itself correctly on the transmitter coil test station 34 viaanother attracting magnet arranged within the unit 30, just below thesurface of the unit, so that the attracting force of the magnetsmaintains the transmitter correctly in place for testing. As is shown inFIG. 2, the transmitter coil test station 34 may include indicia means36, such as a pictorial representation of a transmitter coil that is tobe placed correctly upon the test station 34. By placing the transmittercoil to be tested over this indicia means 36, the transmitter coil isautomatically placed in the appropriate area on the test station 34 fortesting.

Once the coil has been placed upon the test station 34 it is connectedvia a cable to a connecting socket 31 of test station 32. As the coil tobe tested is designed to receive only one type of cable and the cableplug will only fit one of the connecting sockets 34 on test station 32,the unit 30 can then determine the type of coil being tested and canaccess the appropriate test parameters from its stored memory device(discussed in more detail below).

The testing unit 30 also includes an on/off switch 37 and may alsoinclude various indicia means which may aid the tester in using theunit. Such indicia means may include graphics grouping the socketstogether and marking them with descriptive text indicating which cablesthey relate to, as well as similar labelling for the transmitter coiltest station indicating the type of coil to be tested.

FIG. 3 is a functional block diagram of one embodiment of a tester unit30 showing how the system operates in a functional mode. The tester unit30 can be considered to consist of a microcontroller 41, a receiver coilvoltage rectification and current sensing circuit 42, a receiver coil44, a socket voltage driver 43, a cable test circuit 45, a series ofsockets 46, a series of LEDs 35, and an on/off switch 48.

The microcontroller 41 is, in the depicted embodiment, a programmablemicrocontroller that essentially controls the application of testsignals to the appropriate sockets at the appropriate times and alsodigitises and measures the appropriate measurement signals at theappropriate times. An Analogue to Digital Converter (ADC) is built intothe microprocessor 41 to digitise the measurements, and themicroprocessor 41 contains software to compare the measured values tothe known limits which have previously been established for the coiland/or cable being tested and which are stored within a memory of themicroprocessor 41.

The receiver coil voltage rectification and current sensing circuit 42essentially consists of a circuit that measures a parameter related tothe receiver coil current and a rectified voltage inductively induced inthe receiver coil 44 when it is in close proximity to and aligned withthe transmitter coil being tested.

The socket voltage driver 43 activates the sockets and allows thetesting of both the coils and cables to be undertaken by providing eachsocket with the required voltage as dictated by the microcontroller 41.

The cable test circuit 45 monitors the functionality of the cables beingtested by sensing the current being passed therethrough.

The series of sockets 46 allow the coils and/or cables to be connectedto the test unit such that their operation can be tested. Underdirection from the circuit 43, the sockets can be activated and the coiland/or cable tested.

The series of LEDs 35 provide indicators visible to the tester regardingwhether the cables and/or coils being tested meet the requirements. Thiscould include one LED representing a PASS, or a series of LEDsrepresenting a PASS and/or a FAIL.

The on/off switch 48 toggles the power to the system on or off.

The system will now be described in use, with reference to FIGS. 2, 3and 4.

In order to test the operation of a particular transmitter coil, thecoil is placed on the transmitter coil test station 34 where it is heldin place by an alignment magnet that cooperates with the magnet of thetransmitter coil. The alignment magnet is preferably arranged on theinside of the unit housing below the area marked for placement of thetransmitter coil under test, this area being shown in FIG. 2 byreference numeral 36. The purpose of the alignment magnet is to ensurethat the transmitter coil under test is located within a 1mm radius ofits designed position. A cable is then connected from the transmittercoil to a provided socket, shown in FIG. 2 by reference numeral 31, thesocket 31 matching the correct cable connector.

Once the coil and cable are in place, the microcontroller 41 can beactivated to send a signal to the socket voltage driver 43 to drive thecoil with an AC square wave voltage source at or near the resonantfrequency of the coil. This resonant frequency is dependent on the typeof coil being tested, for example in some instances it may be near 2.5or 5.0 MHz. A simple push-pull square wave voltage driver circuit,similar to those used in external speech processors is adequate for thispurpose and is shown in FIG. 4 by reference numeral 43.

If the coil/cable combination plugged into the device is correctlyfunctioning, the circuit will resonate and the coil current will have avalue determined by the coil impedance at its resonant frequency, whichis typically a few tens of Ohms, or less. In testing the coil/cablecombination in accordance with the present invention, the methodinvolves monitoring the coil current and the rectified voltage inducedin the receiver coil 44 close to and aligned with the coil being tested,and if the current and the rectified voltage is found to be outside anacceptable value range, the coil/cable combination passes the test andthe device indicates a PASS to the tester via illuminating the LED 35.If the coil/cable combination is found to be faulty (eg. the coil cableis broken, connector faulty etc) the device indicates a fail by notilluminating the LED, or alternatively, by emitting a FAIL signal viaanother indicator device.

In the event of a failure, most coil/cable combinations either involve acomplete failure of the circuit or a detuning of the circuit in someway. Therefore in these fault conditions, the amplitude of the coilcurrent will be reduced below a predetermined threshold and the coilwill be detected as having failed.

The Receiver Coil Voltage Rectification and Current Sensing Circuit 42measures the compliance of the coil/cable combination and outputs theresult to the microcontroller 41. As mentioned above, one way to testthe coil involves monitoring the current, and this can be done in anumber of different ways.

FIG. 4 depicts a circuit suitable for this purpose in accordance with apreferred embodiment. In FIG. 4, the socket voltage driver is shown as43, the Receiver Coil Voltage Rectification and Current Sensing Circuitis shown as 42, the coil being tested is shown as 53, and the receivercoil is shown as 44.

The microprocessor (not shown in FIG. 4) produces a crystal controlledAC drive signal at or near the resonant frequency of coil 53 (asdescribed above). This signal controls the socket voltage driver circuit43, which consists of a simple push-pull driver as shown. AC currentflowing in the coil 53 induces a mean voltage across the 10 ohm resistorof the Current Sensing Circuit 42, and this voltage is smoothed by the10 uF capacitor. This smoothed voltage is then sent to themicroprocessor 41, being representative of the coil current sensesignal.

The field sense circuit of the Receiver Coil Voltage Rectification andCurrent Sensing Circuit 42 includes a multi-turn coil 44 which is inclose proximity to the coil 53 under test. The AC current flowing in thecoil 53 induces an AC voltage in the adjacent receiver coil 44, and thisvoltage is also rectified and smoothed by the remainder of this circuitand is sent to the microcontroller 41, being representative of the fieldsense signal.

Once the Receiver Coil Voltage Rectification and Current Sensing Circuit42 has taken the measurements representative of the coil current sensesignal and the field sense signal, the microprocessor utilises storedsoftware to determine whether or not the values measured for the coil,correspond to the desired range of values within the designspecification of that particular coil. If these values do fall withinthe design specification range for that coil, a signal is sent to theLED 35 to illuminate and so convey to the user that the device haspassed the test. Otherwise, either a FAIL signal will be conveyed to theuser or the LED 35 will not be illuminated, which is indicative of aFAIL.

FIG. 5 shows a circuit for testing the compliance of a cable only,according to an embodiment of the present invention. In this embodiment,measurements are made by placing a DC potential on one cable lead andmeasuring the potential on another. The other end of the cable isplugged into a resistor load network connecting all the cable leadstogether. When all the cable's leads are functioning normally a specificvoltage, determined by the resistor load network, is expected on thesensed lead 60. If a fault occurs (one line open circuit or shorted toanother) this will change the current flow in the cable and cause thevoltage in the sensed lead 60 to change. The voltage is sensed bydigitising it using the microprocessor 41 ADC and software is used todetermine whether the sensed value corresponds to a normal or a faultycable. When a voltage is sensed which corresponds to a normal cable themicroprocessor 41 illuminates the “PASS” LED 35 in the manner asdiscussed above.

FIG. 5 depicts a test undertaken on a typical two lead cable. In thisexample, if the cable is normal (ie. both leads connected and notshorted), the two resistors create a potential divider and the sensedvoltage is equal to 50% of the supply voltage. If either lead is opencircuit the sensed voltage becomes equal to ground. If the leads areshorted the sensed voltage is equal to the supply rail voltage. Asimilar arrangement can be used for cables with 3 or more leads.

It will be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to the invention as shown inthe specific embodiments without departing from the spirit or scope ofthe invention as broadly described. The present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive.

1. A testing apparatus for testing at least one component of a medicaldevice and diagnosing problems associated therewith, the testingapparatus comprising: at least one testing station for receiving said atleast one component and making an electrical and/or inductive connectionthereto; at least one testing circuit adapted to apply at least one testto said component and measure the response of the component to saidtest; a memory means for storing data indicative of the response to saidtest of at least one equivalent component that is known to beoperational; a comparator means for comparing the response of saidcomponent to said test to said data and determining whether saidresponse is at least substantially similar to said data; and an outputmeans for outputting a result of said comparison.
 2. The testingapparatus of claim I wherein the medical device is a cochlear implantsystem and said at least one component that is to undergo testingcomprises a cable and/or a transmitter coil adapted to be connected toan external speech processor component of said system.
 3. The testingapparatus of claim 1 wherein the apparatus comprises a case having afirst surface having said at least one testing station thereon.
 4. Thetesting apparatus of claim 3 wherein the apparatus is adapted to testmore than type of component.
 5. The testing apparatus of claim 4 whereinthe apparatus is capable of testing at least two different types ofcable and has at least two testing stations for providing an electricalconnection to said cables.
 6. The testing apparatus of claim 5 whereinwhere there are two or cable testing stations, each station is adaptedto test a different type of cable from that of the other cable teststations.
 7. The testing apparatus of claim 6 wherein each cable testingstation comprises a socket having a shape that is adapted to receive aplug of a particular cable design and no other, said socket allowingelectrical connection to the cable under test.
 8. The testing apparatusof claim 3 wherein the apparatus has a single coil testing station. 9.The testing apparatus of claim 8 wherein the coil testing apparatuscomprises a planar area in the first surface of the case on which thetested coil can be placed.
 10. The testing apparatus of claim 9 whereinthe planar area has an indicia means provided thereon that provides anindication of where the tested coil should be placed to ensure anappropriate test of the tested coil is undertaken.
 11. The testingapparatus of claim 10 wherein the indicia means comprises a pictorialrepresentation of a transmitter coil.
 12. The testing apparatus of claim11 wherein the planar area has more than one unique indicia meansprovided thereon.
 13. The testing apparatus of claim 1 wherein a magnetis positioned at or below the planar surface of the case, said magnetadapted to provide magnetic alignment with a magnet within a coil undertest and so maintain the coil in the correct place for testing.
 14. Thetesting apparatus of claim 9 wherein each tested coil has a cableextending therefrom that is also testable by the testing apparatus. 15.The testing apparatus of claim 9 wherein the apparatus is capable ofsensing the type of coil, cable, or coil and cable combination that isunder test and then access from the memory means the appropriate storeddata for use by the comparator means of the apparatus.
 16. The testingapparatus of claim 1 wherein the apparatus further comprises a controlmeans that controls the overall function of the apparatus.
 17. Thetesting apparatus of claim 16 wherein the control means comprises amicrocontroller.
 18. The testing apparatus of claim 17 wherein themicrocontroller further acts as the memory means for the testingapparatus.
 19. The testing apparatus of claim 17 wherein themicrocontroller further comprises a microprocessor having an analogue todigital converter (ADC) to digitise the measurements representative ofthe tested component.
 20. The testing apparatus of claim 17 wherein themeasurements from said one or more testing circuits are in the form ofcurrent and voltage levels and said data indicative of the response ofsaid equivalent operational component is in the form of voltage andcurrent ranges associated with non-faulty cables and transmitter coilsused in cochlear implant systems.
 21. The testing apparatus of claim 1wherein the output means comprises one or more lights that areilluminated or turned off in response to the outcome of the test. 22.The testing apparatus of claim 21 wherein a light illuminates if thetested component passes the test and fails to illuminate if the testedcomponent is inoperative or faulty.
 23. The testing apparatus of claim21 wherein the light is a light emitting diode (LED).
 24. A method oftesting at least one component of a medical device and diagnosingproblems associated therewith comprising the step of making anelectrical and/or inductive connection between said component and atleast one testing station of the testing apparatus as defined in claim 1and performing a test on said component.